add laser pulse tests for propagation through a crystal with gain on and multiple prop_type values

[bruhwiler]

Tested prop_type values should include: n0n2_srw, n0n2_lct, and gain_calc. The tests should be run with 'gain = 1' set and with an n2 value of 16

[gurhar1133]

Should the test have test data? like compare expected pulse.slice.wfr after propagation with actual?

[bruhwiler]

Yes. The initial mesh should be small, like 32 x 32